This invention relates to an acetabular cup assembly for an artificial hip prosthesis. More particularly, the invention is concerned with a three-component acetabular cup assembly for receiving and releasably retaining the femoral head component of a prosthesis.
Artificial hip-joints comprising an endoprosthesis of an acetabulum and an endoprosthesis of a femur are known in the art.
In such prior art prostheses various means for accommodating and retaining the femoral head within the acetabular cup or socket have been disclosed.
For example, U.S. Pat. No. 3,813,699 discloses a hip-joint prosthesis comprising a cup member adapted to snap in place over and holdingly engage a spherical femoral head member. U.S. Pat. No. 3,982,281 discloses a modification of the prosthesis described in U.S. Pat. No. 3,813,699.
U.S. Pat. Nos. 3,863,273; 4,044,403 and 4,172,296 disclose prosthetic hip-joints having various arrangements for retaining the femoral head within the socket member.
U.S. Pat. No. 4,241,463 discloses a prosthetic joint wherein the femoral head is retained within a bearing insert by movement of a split locking ring located intermediate the bearing and the ball-shaped femoral head.
Other arrangements for retaining the femoral head in ball-and-socket joint prosthesis are disclosed in U.S. Pat, Nos. 3,656,184; 3,938,198; 4,030,143; 4,159,544; 4,380,090 and 4,408,360.
U.S. Pat. No. 3,818,512 discloses an artificial hip-joint wherein a femoral head member is locked into an insert member installed within a fixed acetabulum prosthesis, said insert member being screwably fixed into said acetabulum by a self-locking nut.
The above references, which are merely representative, are indicative of the extensive interest in the art to provide successful hip-joint prostheses and, in particular, to provide ball and socket joints which provide maximum articulation and minimum dislocation.
However, none of the prior art prostheses have addressed and successfully resolved the problem not only of retaining the head in the socket but also of easily releasing the head, when required, without impairing the locking facility.
The present invention provides a neat solution to the aforesaid problem by an acetabular cup assembly comprising components having a unique inter-locking and releasable interaction with each other.